A New Fluorescence Immunosensing Method Based on Aptamer-plasmid Complex Amplification

A novel simple, sensitive fluorescence immunosensing method based on aptamer-plasmid complex amplification was developed. This method used the specific recognition between antibody and antigen, as well as aptamer-plasmid complex, and the intercalation of fluorescence dye SYBR Green I in the groove of duplex plasmid DNA in detection of platelet-derived growth factor-BB (PDGF-BB). The immunoassay was performed in the microtiter wells in which rabbit anti-PDGF-BB antibody was immobilized. The PDGF-BB analyte was captured by the primary antibody and then sandwiched by the aptamer-plasmid DNA complex. The introduction of SYBR Green I fluorescence dye allowed for the detection of the sandwiched complex of antibody/antigen/aptamer-plasmid. The optimized salt concentration and ratio of aptamer to PUC19 and SYBR Green I concentration were also analyzed. A linear relationship for the detection of PDGF-BB was at the range from 0.2 to 200 ng ml−1 with a detection limit of 0.1 ng ml−1.